This invention relates to a tracking and monitoring system and, more particularly, to a tracking and monitoring system equipped with heat source tracker used for a penetrating object.
The prior art monitoring system has a human body detecting sensor or a magnet switch. When the human body detecting sensor or the magnet switch founds an invader, the sensor or the switch supplies a detecting signal to a monitor camera, and the monitor camera is directed to the invader. The monitor camera continuously or intermittently takes a moving picture, and stores the image of the invader in magnetic tape or a magnetic disk. The monitor camera may take static pictures at intervals. The images of the static pictures are stored in a photographic film.
When an inspector wants to check the images stored in the magnetic tape or the magnetic disk, the inspector instructs the controller to drive the magnetic tape or the magnetic disk for heading each of the frames, and searches the series of frames for an image to be required. However, a lot of frames are incorporated in the moving picture, and the inspector consumes a large amount of time and labor.
On the other hand, the static pictures are usually less than the frames of the moving picture, and the search is less time-consuming. Moreover, a silver film is usually used as the photographic film, and the image is clearer than those in the frames. However, the image is produced through the development, and the inspector can not promptly search an image to be required.
Another prior art monitoring system is equipped with an electronic still camera. The electronic still camera has a semiconductor memory for storing the images, and pieces of video data representative of the images are supplied from the semiconductor memory to an image reproducing apparatus. An inspector easily searches the semiconductor memory for the image to be required. However, several seconds are consumed for writing a piece of video data information. This is because of the fact that the semiconductor memory is of the type electrically writable non-volatile memory such as an EEPROM (Electrically Erasable and Programmable Read Only Memory). If an invader passes the detectable area within a short time, the prior art monitoring system merely takes several pictures, and an inspector can not clearly discriminate the invader.
Japanese Patent Publication of Unexamined Application No. 11-234653 discloses a monitoring system, which determines the traveling speed of an invader for regulating the recording intervals. The prior art monitoring system is described in detail with reference to the drawings.
FIG. 1 illustrates the first prior art monitoring system. The prior art monitoring system comprises a monitor camera 101 for taking pictures of an invader, a recording unit 102 for storing pieces of video data representative of images of the invader, a velocity sensor 103 for determining the traveling speed of the invader in the field angle xcex8 and a camera controller 109 for controlling the intervals of photographing work. The monitor camera is corresponding to an image pick-up section of the electronic still camera, and a CCD (Charge Coupled Device) is used in the image pick-up section. The monitor camera 101 is directed to the monitoring area, and does not change the direction. However, the field angle covers the monitoring area.
The velocity sensor 103 includes an object detecting sensor 104 and a mode changer 105. The object detecting sensor 104 detects infrared light radiated from a source of heat such as a human body, and produces an object detecting signal S1. The object detecting sensor 104 supplies the object detecting signal S1 to the mode changer 105. The mode changer 105 determines the source of heat to move at a high-speed or a low-speed on the basis of the object detecting signal S1, and selectively supplies mode signals S2 and S3 to the camera controller 109. The camera controller 109 is responsive to the mode signal S2 or S3, and requests the monitor camera 101 to take pictures at high speed or a low speed. The video data are supplied from the monitor camera 101 to the recording unit 102, and are stored in the recording unit 102.
The object detecting sensor 104 has a differential infrared detector 106, an optical element 107 and a signal processing unit 108. The differential infrared detector 106 produces detecting signals at intervals, and the signal processing unit 108 produces the object detecting signal S1 from the detecting signals.
The differential infrared detector 106 is implemented by a pair of pyroelectric infrared detecting elements 106a/106b, and the pyroelectric infrared detecting elements 106a and 106b are connected in such a manner as to be opposite in polarity. For this reason, the pyroelectric infrared detecting elements 106a/106b serve as the differential infrared detector 106. The optical element 107 is implemented by a Fresnel lens, and the Fresnel lens 107 directs incident light from the detecting areas E1, E2, E3, E4 and E5 to the pyroelectric infrared detecting elements 106a/106b. Thus, the Fresnel lens 107 makes the monitor camera 101 have a coverage as wide as the monitoring area.
The detecting areas E1 to E5 are spaced from one another, and the optical element 107 assigns all of the detecting areas E1 to E5 to the object detecting sensor 104. Each of the detecting areas E1 to E5 contains two sub-areas e1 and e2, and the sub-areas e1 and e2 are assigned to the pyroelectric infrared detecting elements 106a/106b, respectively. When a heat source is in the sub-areas e1, the pyroelectric infrared detecting element 106a produces a detecting signal, and supplies the detecting signal to the signal processing unit 108. On the other hand, when the heat source is in the sub-areas e2, the pyroelectric infrared detecting element 106b produces a detecting signal, and supplies the detecting signal to the signal processing unit 108. The detecting signal from the pyroelectric infrared detecting element 106a is opposite in polarity to the detecting signal from the other pyroelectric infrared detecting element 106b. 
The signal processing unit 108 includes a signal processing circuit, an amplifier, a reference level generator and a level detector. The differential infrared detector 106 is connected to the signal processing circuit, and supplies the detecting signals to the signal processing circuit. The signal processing circuit is connected to the amplifier, and the detecting signals are amplified by the amplifier. The reference level generator produces a pair of reference signals, and the pair of reference signals is indicative of a positive threshold level and a negative threshold level. The amplifier and the reference level generator are connected to the level detector, and the level detector compares the detecting signals with the reference signal. When the detecting signals exceed the threshold level, the level detector changes the object detecting signal S1 to an active high level, and keeps the detecting signals at the threshold levels in so far as the detecting signals exceed the threshold levels. Thus, the level detector produces the object detecting signal S1 from the detecting signals indicative of the source of infrared light.
Assuming now that a human body walks in the monitoring field as indicated by arrow M, the human body radiates infrared light, and crosses the detecting areas E1 to E5. While the human body is crossing each of the detecting areas E1 to E5, the human body firstly enters the sub-area e1, thereafter, exiting from the sub-area e1, entering the sub-area e2, finally exiting from the sub-area e2. When the human body enters the sub-area e1, the pyroelectric infrared detecting element 106a detects the infrared light, and changes the detecting signal to the positive level as shown in FIG. 2. Thereafter, the human body exits from the sub-area e1, and the pyroelectric infrared detecting element 106a recovers the detecting signal from the positive level to the ground level. The level detector compares the detecting signal with the positive threshold level. While the detecting signal is exceeding the positive threshold level, the level detector changes the object detecting signal to the positive high level. Thus, the level detector shapes the waveform, and produces the first pulse S1.
Subsequently, the human body enters the sub-area e2, and the pyroelectric infrared detecting element 106b changes the detecting signal to the negative level. When the human body exits from the sub-area e2, the pyroelectric infrared detecting element 106b recovers the detecting signal from the negative level to the ground level. The level detector also compares the detecting signal with the negative threshold level, and produces the second pulse S1. Thus, while the human body is crossing each of the detecting areas E1, E2, E3, E4 and E5, the signal processing unit 108 outputs two pulses S1 as the object detecting signal. The signal processing unit 108 supplies the object detecting signal S1 to the mode changer 105.
The mode changer 105 stores a reference time period T therein. The reference time period T is variable, and a watchman manually regulates the reference time period T to a certain value appropriate to the traveling velocity of an object. The mode changer 105 firstly determines a pulse interval t1/t2 of the object detecting signal S1, and compares the pulse interval t1/t2 with the reference time period T to see whether or not the pulse interval t1/t2 is longer than the reference time period T. The pulse interval t1 is longer than the reference time period T. Then, the mode changer 105 produces the mode signal S2 representative of a low-speed photographing work. On the other hand, the pulse interval t2 is shorter than the reference time period T. Then, the mode changer 105 produces another mode signal S3 representative of a high-speed photographing work.
The mode signal S2 or S3 is supplied to the camera controller 109, and the camera controller 109 instructs the monitor camera 101 to take pictures at long time intervals or at short time intervals. The monitor camera 101 takes the pictures of a low-speed moving object at the long time intervals and the pictures of a high-speed moving object at the short time intervals. The pieces of video data are transferred to the recording unit 102, and are stored in the non-volatile memory. The pieces of video data are read out from the non-volatile memory, and the image of the human body is produced on a display panel. Thus, the prior art monitoring system changes the photographing work between the high speed and the low speed depending upon the traveling speed of the moving object.
Another prior art tracking and monitoring system is disclosed in Japanese Patent Publication of Unexamined Application No. 11-258043. The second prior art tracking and monitoring system is hereinbelow described with reference to FIG. 3. The second prior art tracking and monitoring system is installed partially in a field and partially in a monitor room.
A camera unit is installed in the field, and includes an infrared industrial television camera 201, a pan head 202, a pair of electric motors 203a/203b and a motor driver 204. The infrared industrial television camera 201 is attached to the pan head 202, and the pan head 202 permits the infrared industrial television camera 201 to three-dimensionally change the attitude thereof. The electric motors 203a/203b are connected to a two-axis driving mechanism of the pan head 202, and the motor driver 204 is electrically connected to the electric motors 203a/203b. The motor driver 204 selectively energizes the electric motors 203a/203b, and the pan head 202 directs the infrared industrial television camera 201 to a desired direction. The infrared industrial television camera 201 detects infrared light radiated from a source of heat, and produces a video signal representative of the image in the field of view.
A monitoring apparatus is installed in the monitor room, and includes a signal processing unit 205, an image processing unit 206, a switch unit 207, a display unit 208 and a controller 209. The infrared industrial television camera 201 is connected to the signal processing unit 205, and supplies the video signal to the signal processing unit 205. The signal processing unit 205 is connected to the display unit 208 and the image processing unit 206, and processes the video signal. The signal processing unit 205 supplies an image-carrying signal to the display unit 208, and the display unit 208 reproduces the image in the field of view. A watchman checks the display unit 208 to see whether or not any invader enters the monitoring area of the second prior art tracking and monitoring system.
The signal processing unit 205 further supplies a video signal to the image processing unit 206. The image processing unit 206 forms a tracking loop together with the motor driver 204, the electric motors 203a/203b, the infrared industrial television camera 201 and the signal processing unit 205. The image processing unit 206 recognizes the image of the invader in the field of view, and determines the amount of offset between the image and the center of the field of view. The image processing unit 206 determines how to move the infrared industrial television camera 201 in order to decrease the amount of offset, and supplies a control signal through the switch unit 207 to the motor driver 204. The motor driver 204 selectively energizes the electric motors 203a/203b so as to cause the infrared industrial television camera 201 to track the invader.
When the watchman wants to manually control the infrared industrial television camera 201, the switch unit 207 is changed, and the controller 209 is electrically connected through the switch unit 207 to the motor driver 204. The watchman manipulates the controller 209, and the motor driver 204 causes the electric motors 203a/203b to direct the infrared industrial television camera 201 to a desired direction.
Problems are encountered in the first prior art monitoring system in grate price and in the adjustment of the time period T. Although the first prior art monitoring system is expected to monitor the wide monitoring area, the monitor camera 101 does not change the direction. The optical element 107 or the Fresnel lens widens the field angle xcex8, and is indispensable in so far as the monitor camera 101 is not accompanied with any three-dimensional driving mechanism. Moreover, the first prior art monitoring system is expected to change the photographing work between the high speed and the low speed, and requires the signal processing unit 108 and the mode changer 105 for estimating the traveling speed. The signal processing unit 108 and the mode changer 105 are also indispensable from the viewpoint that the photographing work is to be changed between the high speed and the low speed. The Fresnel lens 107, the signal processing unit 108 and the mode changer 105 are expensive, and increase the price of the first prior art monitoring system.
The first prior art monitoring system is not designed for a particular invader. In other words, the traveling speed is unknown to the manufacturer. For this reason, the user needs to adjust the time period T to an appropriate value. The user is to determine the appropriate value in the trial and error fashion, and the adjustment of the time period T is complicated and time-consuming.
On the other hand, a problem inherent in the second prior art tracking and monitoring system is great price. The image processing unit 206 is expected to accurately determine the amount of offset between the image of the invader and the center of field of view. The accuracy is dependent on the integration density of the infrared detecting element array. Such a high density infrared detecting element array is expensive. Moreover, the image processing unit 206 runs on a huge complicated computer program for processing the video data, and a high-speed data processor is required for the execution of the huge complicated computer program. Such a huge complicated computer program and the high-speed data processor are expensive, and make the second prior art tracking and monitoring system great price.
It is therefore an important object of the present invention to provide a tracking and monitoring system, which is economical and improved in manipulability.
In accordance with an aspect of the present invention, there is provided a tracking and monitoring system comprising a heat source tracker producing a data signal representative of a current position of the heat source in a field of view and three-dimensionally changing the attitude thereof in such a manner as to catch an image of the heat source at a predetermined position in the field of view for tracking the heat source in a monitoring zone, a data processing system connected to the heat source tracker, checking the data signal to see whether or not the heat source enters a prohibited zone defined in the monitoring zone and producing an instruction for an alarm when the heat source enters the prohibited zone, and an alarm unit connected to the data processing system and responsive to the instruction for giving the alarm.